The purpose of this investigation is to elucidate the function of basophils and mast cells in cell-mediated hypersensitivity reactions, particularly with regard to an understanding of the role of these cells in immunologic tumor rejection. The experiments proposed will make use of a tissue culture system and will employ a combined morphologic, immunologic, and biochemical approach to determine: 1. Whether sensitized lymphocytes or their products affect pharmacologic mediator (histamine) synthesis and/or release in basophils/mast cells, or, conversely, whether basophils modulate lymphocyte function. 2. The mechanism(s) of mediator release from basophils in both physiological and pathological circumstances, and as mediated by cellular or humoral pathways. 3. The fate of basophils in tissue culture anaphylactic degranulation. 4. The effects of basophils and their pharmacologic mediators on tumor cells. 5. The effects of basophil ablation, induced by a specific anti-serum, on the expression of cellular immunity.